Income Taxes Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount									$ 553	$ 488	$ 436
Effective Income Tax Rate Reconciliation, Change in Unrecognized Tax Benefits									(161)	(5)	(63)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount									51	(25)	(47)
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount									35	38	48
Effective Income Tax Reconciliation, Foreign Capital Loss									(15)	(13)	(27)
Effective Income Tax Rate Reconciliation, Equity in Earnings (Losses) of Unconsolidated Subsidiary, Amount									7	14	31
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount									0	0	(39)
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount									0	(1)	(18)
Income Tax Expense (Benefit)	$ 134	$ 130	$ 56	$ 150	$ 155	$ 144	$ 94	$ 103	$ 470	$ 496	$ 321